CH 8

Question 1

the classic experiment

Answer 1

examines effect of independent variable (stimuli) on the dependent variable

Question 2

How is the independent variable created in a classical experiment

Answer 2

by randomly assigning subjects to an experimental or control group and then introducing the experimental stimuli to the experimental group subject

Question 3

what is expected in a classic experiment and what is the design classified as?

Answer 3

one the experimental group group will change from pre- to post test.

the design is classified as a two group pretest/ post-test design

Question 4

What is a double blind design?

Answer 4

neither the subject nor the experimenters know the membership of the experimental and control groups

Question 5

what do experimental designs require?

what are the three ways this is accomplished?

Answer 5

they require experimental and control groups be comparable

1. Probability sampling
2. randomization
3. matching

Question 6

3 ways experimental designs make experimental and control groups comparable

1. probability sampling

Answer 6

experimental and control groups would be create by randomly selecting subjects from a sampling frame (approach rarely used)

Question 7

3 ways experimental designs make experimental and control groups comparable

2. randomization

Answer 7

the primary method used to create comparable groups. a sample of subjects is obtained (through convenience sampling) and then each subject in this non probability sample is randomly assigned to an experimental or control group

Question 8

3 ways experimental designs make experimental and control groups comparable

3. matching

Answer 8

subjects are measured on variables thought to affect the dependent variable or on the dependent variable itself (in a pretest) similar (matched) subjects are identified and then randomly assigned to the experimental group and three to the control group

Question 9

pre experimental designs

Answer 9

weak designs that lack a control group for comparison

ex: one shot case study/ single case study/static group comparison
(all 3 designs should be avoided they lack internal validity- can’t handle history, maturation and testing effects)

Question 10

Solomon four group design

Answer 10

A powerful experimental design

includes two experimental groups and two control groups (only one of experimental and control group is pretested)

it can asses the potential of an interaction between testing (the pretest) and the experimental stimuli

Question 11

what are some threats to internal validity

Answer 11

1. statistical regression: have a nonrandom sample from a population and two measures that are imperfectly correlated
2. selection bias:
   proper randomization is not achieved
3. attrition/experimental mortality:
   Participants frequently drop out of experiments whilst they are taking place/before they finish
4. demoralization: those in the control group become resentful of not receiving the experimental treatment.

Question 12

what are natural experiments

Answer 12

when scientist take advantage of events that occur in the real world.
these are less artificial than laboratory studies but lack the experimental control that can be achieved in a laboratory setting